A Numerical Simulation and Diagnostic Analysis of Mesoscale System on the Heavy Rainfall over the Yangtze River

Using the mesoscale model of the MM5,the mesoscale numerical simulation of the heavy rainfall of the Jianghuai Mei-yu front during 7-9 Sep 2007 was carried out.According to the data from routine meteorological observation and precipitation data of surface ground,a particular analysis of the mesoscale system of the heavy rainfall had been made.The major results were as follows: MCSs propagated eastwardly,which developing on Mei-yu front,was the direct influent system of the rainstorm.The pressure in the middle-lower troposphere drops under the effect of the positive vortex advection around the shear line,which generated allobaric wind convergence and then led to ascending motion.The lift-up of warm and humid air current in the lower troposphere triggered the bursting-out of instable convective energy,which led to form local convection and heavy rain.